A 19-year-old woman died beneath the wheels of a V train in Queens yesterday after trying to retrieve the cell phone she dropped onto the subway tracks, police said.

Lina Vallegas of 83rd Street made her way down to the Manhattan-bound tracks at the Grand Avenue station at about 2 p.m. after dropping her phone, officials said.

The spot where it landed was about a train-car length from the end of the platform where the subway enters the station.

MTA sources said the teenager never had a chance when the rumbling V train came around a blind corner.

At the train’s usual speed of 25 mph, the train operator only had about five seconds to stop from the time it came around the bend to the time it reached the spot where Vallegas was trying to grab her phone.

“You can’t do anything once that train comes,” said a supervisor for the MTA’s emergency response team. “By the time you see the train, it’s too late.”

Vallegas was killed instantly by the first car. The accident snarled Queens subway traffic as trains were slowed and the usually local running V train was forced to run express between Forest Hills and Roosevelt Avenue for more than an hour and a half.

MTA spokeswoman Marisa Baldao warned commuters not to venture on the tracks if they drop personal belongings from the platform – which can be as high as 4 feet 9 inches up from the track bed.

“We do advise to go to a token booth or find transit authority personal, but never go on to the track yourself,” she said. Passengers may also call 311 city information for help with items in the tracks.

The MTA supervisor who spoke to The Post on condition of anonymity said that, while nonsuicide deaths on the tracks are rare, he’s often seen people who ignore warnings and travel down into the train bed.

“A lot of people do that,” he said. “I’ve seen people walking in the middle of the tunnel who don’t want to wait for the next train.”

The most recent accidental subway death came last December, when a man fell into the tracks in Greenwich Village and was hit by an uptown No. 1 train at the Christopher Street and Seventh Avenue station.